CN115009287A

CN115009287A - Vehicle speed calculation device and control device for vehicle

Info

Publication number: CN115009287A
Application number: CN202210197089.XA
Authority: CN
Inventors: 小寺隆志; 高岛亨; 西村公一; 石野嵩人
Original assignee: JTEKT Corp; Toyota Motor Corp
Current assignee: JTEKT Corp; Toyota Motor Corp
Priority date: 2021-03-04
Filing date: 2022-03-01
Publication date: 2022-09-06
Also published as: EP4052981A1; JP2022135156A; US20220289205A1; US11964665B2

Abstract

The invention discloses a vehicle speed calculation device and a control device for a vehicle. A vehicle speed calculation device includes a vehicle speed calculation unit (200), the vehicle speed calculation unit (200) being configured to calculate a control vehicle speed obtained by estimating a vehicle body speed as a speed at which a vehicle actually travels, as a state variable for controlling an in-vehicle device configured to operate to implement various functions provided in the vehicle. The vehicle speed calculation unit (200) is configured to include: an extracting function of extracting, from among wheel speeds of the plurality of wheels, at least one wheel speed obtained from at least one wheel assumed to rotate in a state where an influence causing a difference from a vehicle body speed is likely to be small; and a calculation function of calculating a control vehicle speed based on the at least one wheel speed extracted by the extraction function.

Description

Vehicle speed calculation device and control device for vehicle

Technical Field

The invention relates to a vehicle speed calculation device and a control device for a vehicle.

Background

Various functions provided in the vehicle include, for example, a function of steering a steered wheel of the vehicle. Japanese unexamined patent application publication No. 2020-69862 (JP 2020-69862A) discloses a steer-by-wire steering system as a means for realizing a function of steering steered wheels of a vehicle.

The steering system described in JP 2020-69862A includes a control device that controls the operation of the steering system. Such a control device is configured to control the operation of the steering system based on a vehicle speed (hereinafter referred to as "control vehicle speed") among various information obtained from the vehicle. In the control device, the control vehicle speed is obtained as an average value of wheel speeds of steered wheels obtained from front wheel sensors provided in the vehicle.

Disclosure of Invention

Here, in JP 2020-69862A, the control of the vehicle speed obtained as described above is used for various controls in the vehicle and control of the operation of the steering system. The control vehicle speed usually obtained in a vehicle is obtained by estimating a vehicle body speed as a speed at which the vehicle actually travels. Therefore, the vehicle body speed and the control vehicle speed obtained by estimating the vehicle body speed may differ from each other according to the rotation state of the wheel from which the control vehicle speed is obtained.

For example, a method of performing filtering processing when obtaining the control vehicle speed may be used to reduce the difference between the vehicle body speed and the control vehicle speed. This method is effective in the case where the difference between the vehicle body speed and the control vehicle speed is relatively large, but in the case where the difference is relatively small, the method reduces the ability to follow the change in the control vehicle speed in various controls in the vehicle using the control vehicle speed. That is, there is a trade-off relationship between reducing the difference between the vehicle body speed and the control vehicle speed and suppressing a decrease in the ability to follow a change in the control vehicle speed in various controls in the vehicle using the control vehicle speed.

According to an aspect of the present invention, there is provided a vehicle speed calculation device including a vehicle speed calculation unit configured to calculate a control vehicle speed obtained by estimating a vehicle body speed that is a speed at which a vehicle actually travels, as a state variable for controlling an in-vehicle device configured to operate to implement various functions provided in the vehicle. The vehicle speed calculation unit is configured to include: an extraction function that extracts, from among a plurality of wheel speeds of a plurality of wheels, at least one wheel speed obtained from at least one wheel assumed to rotate in a state where an influence that causes a difference from a vehicle body speed is likely small; and a calculation function of calculating a control vehicle speed based on the at least one wheel speed extracted by the extraction function.

With this configuration, at least one wheel speed is actively considered in calculating the control vehicle speed. At least one wheel speed is obtained from at least one wheel assumed to rotate in a state where the influence causing the difference from the vehicle body speed may be small, from among a plurality of wheels rotating in a state where there are large and small influences causing the difference from the vehicle body speed. This is achieved by the extraction function of the vehicle speed calculation unit. Therefore, the difference between the control vehicle speed calculated by the function of the vehicle speed calculation unit and the vehicle body speed is reduced so that the difference becomes small. That is, for example, it is not necessary to reduce the difference between the vehicle body speed and the control vehicle speed by adopting a method of performing filtering processing when obtaining the control vehicle speed. In this case, it is possible to achieve both reduction of the difference between the vehicle body speed and the control vehicle speed and suppression of a decrease in the ability to follow a change in the control vehicle speed in various controls in the vehicle using the control vehicle speed.

Here, the wheel speed obtained from the wheel in a slip state in which the wheel is spinning with respect to the ground contact surface as a rotation state of the wheel may be larger than the wheel speed obtained from the wheel not in a slip state in which there is a high possibility that the wheel speed obtained from the wheel in a slip state is different from the vehicle body speed. On the other hand, the wheel speed classified as a small value in the case where the values of the plurality of wheel speeds are classified according to the magnitude thereof is low in the possibility of being a value obtained from the wheel in the slip state.

Therefore, in the vehicle speed calculation device according to the aspect, the extraction function may be configured to extract at least one wheel speed classified into at least one small value in a case where the values of the plurality of wheel speeds are classified according to the magnitudes thereof.

With this configuration, for example, even in the case where the plurality of wheels include a wheel in a slipping state, at least one wheel speed obtained from at least one wheel not in a slipping state can be positively considered in calculating the control vehicle speed. This is effective for reducing the difference between the vehicle body speed and the control vehicle speed.

Here, the wheel speed obtained from the wheel in the locked state as the rotation state of the wheel may be smaller than the wheel speed obtained from the wheel not in the locked state, and the possibility that the wheel speed obtained from the wheel in the locked state is different from the vehicle body speed is high. On the other hand, at least one wheel that is unlikely to fall into the locked state among the plurality of wheels is determined in advance in the design of the vehicle.

Therefore, in the vehicle speed calculation device according to the aspect, the extraction function may be configured to extract at least one wheel speed of at least one wheel that is determined in the design of the vehicle to be unlikely to fall into the locked state, the locked state of each of the plurality of wheels being a state in which the wheel does not rotate relative to the ground contact surface even while the vehicle is running.

With this configuration, for example, even in the case where the plurality of wheels includes a wheel in a locked state, at least one wheel speed obtained from at least one wheel that is not in the locked state can be positively considered in calculating the control vehicle speed. This is effective for reducing the difference between the vehicle body speed and the control vehicle speed.

In the vehicle speed calculation device according to the aspect, the extraction function may include: a first extraction function of extracting at least one wheel speed classified into at least one small value in a case where values of a plurality of wheel speeds are classified according to the magnitude thereof, and a second extraction function of extracting at least one wheel speed of at least one wheel determined in the design of the vehicle to be unlikely to fall into a locked state. The vehicle speed calculation unit may be configured to calculate the control vehicle speed based on at least one of a first vehicle speed obtained from the at least one wheel speed extracted by the first extraction function and a second vehicle speed obtained from the at least one wheel speed extracted by the second extraction function.

With this configuration, for example, the control vehicle speed may be calculated based on the first vehicle speed in a case where it is assumed that there is a wheel in a slipping state, and the control vehicle speed may be calculated based on the second vehicle speed in a case where it is assumed that there is a wheel in a locked state. Therefore, the difference between the vehicle body speed and the control vehicle speed can be effectively reduced.

In the vehicle speed calculation device according to the aspect, the vehicle speed calculation unit may be configured to further include: a vehicle speed distribution function that sums a plurality of vehicle speeds including a first vehicle speed obtained by the first extraction function and a second vehicle speed obtained by the second extraction function at a predetermined distribution ratio. The vehicle speed distribution function may include: a function of changing the distribution ratio according to the acceleration-deceleration state of the vehicle, and a function of gradually changing the distribution ratio when changing the distribution ratio.

With this configuration, since the possibility that the wheel falls into the slip state or the locked state changes according to the acceleration-deceleration state of the vehicle, the distribution ratio is changed according to the acceleration-deceleration state of the vehicle. When the distribution ratio is actually changed, the control vehicle speed obtained as a result of the calculation may suddenly change between before the change of the distribution ratio and after the change of the distribution ratio. With the above-described configuration, even in the case where the distribution ratio is changed, it is possible to suppress an abrupt change in the control vehicle speed obtained as a result of the calculation between before the change in the distribution ratio and after the change in the distribution ratio.

The vehicle speed calculation device according to the aspect may be used for a control device of a vehicle configured to control an operation of the vehicle-mounted device using a control vehicle speed obtained by the vehicle speed calculation device. In this case, a control device for a vehicle may be provided, which can achieve both reduction of the difference between the vehicle body speed and the control vehicle speed and suppression of a decrease in the ability to follow a change in the control vehicle speed in various controls in the vehicle using the control vehicle speed.

With the vehicle speed calculation device and the control device for a vehicle according to the aspects of the invention, it is possible to achieve both reduction of the difference between the vehicle body speed and the control vehicle speed and suppression of a decrease in the ability to follow a change in the control vehicle speed in various controls in a vehicle using the control vehicle speed.

Drawings

Features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which like reference numerals represent like elements, and wherein:

fig. 1 is a diagram schematically showing the configuration of a steer-by-wire steering system;

FIG. 2 is a block diagram showing the function of the steering control device;

fig. 3 is a block diagram showing the function of a steering force calculation unit in the steering side control unit;

fig. 4 is a block diagram showing the function of an axial force calculation unit in the steering side control unit;

fig. 5 is a block diagram showing the function of a restriction processing unit in the steering-side control unit;

fig. 6 is a block diagram showing the function of a pinion angle feedback control unit in the steering side control unit;

fig. 7 is a block diagram showing the function of a vehicle speed calculation unit in the steering-side control unit according to the first embodiment;

fig. 8 is a block diagram showing the function of a first vehicle speed calculation unit in the vehicle speed calculation unit according to the first embodiment;

fig. 9 is a block diagram showing the function of a second vehicle speed calculating unit in the vehicle speed calculating unit according to the first embodiment;

fig. 10 is a block diagram showing the function of an abnormal wheel speed replacement unit in the first vehicle speed calculation unit of the vehicle speed calculation unit according to the second embodiment.

Detailed Description

First embodiment

A vehicle speed calculation device and a control device for a vehicle according to a first embodiment will be described below with reference to the drawings. As shown in fig. 1, the steering system 2 according to the embodiment is configured as a steer-by-wire steering system. The steering system 2 includes a steering control device 1, and the steering control device 1 is a control device for a vehicle and is configured to control the operation of the steering system 2. The steering system 2 includes a steering mechanism 4 that is steered by a driver using a steering wheel 3, and a steering mechanism 6 that steers left and right steered

wheels

5L and 5R in accordance with a steering operation input to the steering mechanism 4 by the driver. The steered

wheels

5L and 5R are left and right front wheels arranged on the front side of the vehicle. The steering system 2 according to this embodiment has a structure in which the power transmission path between the steering mechanism 4 and the steering mechanism 6 is normally mechanically cut off. In this embodiment, the steering system 2, i.e., the steering mechanism 4 and the steering mechanism 6, is an example of an in-vehicle device configured to operate to implement various functions provided in a vehicle.

The steering mechanism 4 includes a steering shaft 11 and a steering-side actuator 12. The steering shaft 11 is connected to the steering wheel 3. The steering-side actuator 12 includes a steering-side motor 13 and a speed reduction mechanism 14. The steer-side motor 13 applies a steer reaction force as a force against steer operation to the steering wheel 3 via the steer shaft 11. The steer-side motor 13 is connected to the steer shaft 11 via, for example, a reduction mechanism 14 including a worm and a worm wheel.

The steering mechanism 6 includes a first pinion shaft 21, a rack shaft 22 as a steering shaft, and a rack housing 23. The first pinion shaft 21 and the rack shaft 22 are connected at a predetermined crossing angle. The rack and pinion mechanism 24 is configured by meshing the pinion teeth 21a formed in the pinion shaft 21 and the rack teeth 22a formed in the rack shaft 22 with each other. That is, the pinion shaft 21 is an example of a rotation shaft whose rotation angle can be converted into the steering angle of the steered

wheels

5L and 5R. The rack housing 23 accommodates a rack and pinion mechanism 24. An end of the pinion shaft 21 opposite to the side connected to the rack shaft 22 protrudes from the rack housing 23. Both ends of the rack shaft 22 protrude from both ends of the rack housing 23 in the axial direction, respectively. The tie rods 26 are connected to the ends of the rack shaft 22 via respective rack ends 25, each of said rack ends 25 being formed by a ball joint. The distal ends of the tie rods 26 are connected to knuckles (not shown), respectively, to which the left and right steered

wheels

5L and 5R are fitted, respectively.

The steering mechanism 6 includes a steering-side actuator 31. The steering-side actuator 31 includes a steering-side motor 32, a transmission mechanism 33, and a conversion mechanism 34. The steering-side motor 32 applies a steering force for steering the steered

wheels

5L and 5R to the rack shaft 22 via a transmission mechanism 33 and a conversion mechanism 34. The turning-side motor 32 transmits the rotation to the conversion mechanism 34 via a transmission mechanism 33 formed of, for example, a belt transmission mechanism. The transmission mechanism 33 converts the rotation of the steering-side motor 32 into the reciprocating motion of the rack shaft 22 via a conversion mechanism 34 formed of, for example, a ball screw mechanism.

In the steering system 2 having the above-described configuration, the motor torque is applied as a steering force from the steering-side actuator 31 to the rack shaft 22 in accordance with the operation of the steering wheel by the driver, thereby changing the steering angle of the steered

wheels

5L and 5R. At this time, a steering reaction force as a force against the steering operation by the driver is applied from the steering-side actuator 12 to the steering wheel 3. That is, in the steering system 2, the steering torque Th required for steering the steering wheel 3 is changed by the steering reaction force as the motor torque applied from the steering-side actuator 12.

The pinion shaft 21 is provided because the rack shaft 22 is supported in the rack housing 23 together with the pinion shaft 21. That is, the rack shaft 22 is supported to be movable in the axial direction thereof and pressed toward the pinion shaft 21 by a support mechanism (not shown) provided in the steering system 2. Thus, the rack shaft 22 is supported in the rack housing 23. Another support mechanism that supports the rack shaft 22 in the rack housing 23 without using the first pinion shaft 21 may be provided.

Electrical arrangement of a steering system 2

As shown in fig. 1, the steering side motor 13 and the steering side motor 32 are connected to the steering control device 1. The steering control device 1 controls the operations of the motor 13 and the motor 32 by controlling the supply of electric current as control values of the motor 13 and the motor 32.

The torque sensor 41, the steering-side rotation angle sensor 43, and the steering-side rotation angle sensor 44 are connected to the steering control device 1. The torque sensor 41 detects a steering torque Th that is a value indicating a torque applied to the steering shaft 11 in accordance with the steering manipulation by the driver. The torque sensor 41 is provided on the steering shaft 11 at a position closer to the steering wheel 3 than the speed reduction mechanism 14. The torque sensor 41 detects the steering torque Th based on the torsion amount of the torsion bar 42 provided in the intermediate portion of the steering shaft 11. For example, the steering torque Th is detected as a positive value when the rightward steering is performed, and is detected as a negative value when the leftward steering is performed.

The steering-side rotation angle sensor 43 detects a rotation angle θ a, which is an angle of the rotation shaft of the steering-side motor 13, as an angle in a range of 360 °. The steering-side rotation angle sensor 43 is provided in the steering-side motor 13. The rotation angle θ a of the steering-side motor 13 is used to calculate a steering angle θ s. The steer-side motor 13 and the steer-shaft 11 are operated in conjunction with each other via the reduction mechanism 14. Therefore, the rotation angle θ a of the steering-side motor 13 has a correlation with the rotation angle of the steering shaft 11 or the steering angle θ s, which is the rotation angle of the steering wheel 3. Therefore, the steering angle θ s can be calculated based on the rotation angle θ a of the steering-side motor 13. For example, when the right-hand steering manipulation is performed, the rotation angle θ a is detected as a positive value, and when the left-hand steering manipulation is performed, the rotation angle θ a is detected as a negative value.

The steering side rotation angle sensor 44 detects a rotation angle θ b, which is an angle of a rotation shaft of the steering side motor 32, as an angle in a range of 360 °. The steering side rotation angle sensor 44 is provided in the steering side motor 32. The rotation angle θ b of the steering-side motor 32 is used to calculate the pinion angle θ p. The steering-side motor 32 and the pinion shaft 21 are operated in conjunction with each other via the transmission mechanism 33, the conversion mechanism 34, and the rack and pinion mechanism 24. Therefore, the rotation angle θ b of the steering-side motor 32 and the pinion angle θ p as the rotation angle of the pinion shaft 21 have a correlation. Therefore, the pinion angle θ p can be calculated based on the rotation angle θ b of the steering-side motor 32. The pinion shaft 21 meshes with the rack shaft 22. Therefore, the pinion angle θ p and the amount of movement of the rack shaft 22 have a correlation. That is, the pinion angle θ p is a value reflecting the state of the steering mechanism 6 as the steering angle of the steered

wheels

5R and 5L. The rotation angle θ b is detected as a positive value when the rightward steering manipulation is performed, and is detected as a negative value when the leftward steering manipulation is performed.

The brake control device 45 is connected to the steering control device 1 via an unillustrated in-vehicle network such as CAN. The brake control device 45 is provided in the vehicle separately from the steering control device 1. The brake control device 45 controls the operation of a brake device (not shown) mounted in the vehicle. The left front wheel speed sensor 47l and the right front wheel speed sensor 47r are connected to the brake control device 45.

The left front wheel speed sensor 47L detects a left front wheel speed Vfl of the steered wheel 5L as a left front wheel. The right front wheel speed sensor 47R detects a right front wheel speed Vfr of the steered wheel 5R as the right front wheel. The front wheel speed sensors 47L and 47R are sensor hubs provided in a hub unit, which is a bearing unit (not shown) configured to support the steered

wheels

5L and 5R with respect to the vehicle body such that the steered

wheels

5L and 5R are rotatable.

The left rear wheel speed sensor 48l and the right rear wheel speed sensor 48r are connected to the brake control device 45. The left rear wheel speed sensor 48l detects a left rear wheel speed Vrl of a left rear wheel among right and left rear wheels (not shown) provided on the rear side of the vehicle. The right rear wheel speed sensor 48r detects a right rear wheel speed Vrr of a right rear wheel among right and left rear wheels (not shown) provided on the rear side of the vehicle. The rear wheel speed sensors 48l and 48r are sensor hubs provided in a hub unit, which is a bearing unit (not shown) configured to support the rear wheel with respect to the vehicle body such that the rear wheel is rotatable. The steering system 2 according to the embodiment is mounted in a vehicle having a so-called FR system in which power generated by a drive source, such as an engine or a motor, mounted on the front side of the vehicle is used to generate drive torque for rotationally driving the right and left rear wheels. That is, the right and left rear wheels are driving wheels that are driven to generate driving force required for the vehicle to travel.

The wheel speeds Vfl, Vfr, Vrl, and Vrr are input to the brake control device 45. The brake control device 45 is configured to output the wheel speeds Vfl, Vfr, Vrl, and Vrr to the steering control device 1.

The stop lamp switch 49 is connected to the brake control device 45. In the case where an operation of a brake pedal Bp installed in the vehicle is detected, the brake control device 45 controls the on/off state of a stop lamp installed at the rear of the vehicle such that the stop lamp is in the on state by turning on a stop lamp switch 49. In the case where the operation of the brake pedal Bp is not detected, the brake control device 45 controls the on/off state of the stop lamp so that the stop lamp is in the off state by turning off the stop lamp switch 49. The brake control device 45 generates a stop lamp signal S as information indicating the on/off state of the stop lamp. The stop lamp signal S is information indicating whether the brake pedal Bp is being operated, i.e., whether the vehicle is in a decelerating state among acceleration-deceleration states of the vehicle. When the stop lamp switch 49 is turned on, the brake control device 45 generates a stop lamp signal S indicating the on state. When the stop lamp switch 49 is off, the brake control device 45 generates a stop lamp signal S indicating an off state. The brake control device 45 is configured to output a stop lamp signal S to the steering control device 1.

Function of steering control device 1

The steering control device 1 includes a Central Processing Unit (CPU) and a memory, not shown, and the CPU executes a program stored in the memory at intervals of a predetermined operation cycle. Thus, various processes are performed.

Some processes performed by the steering control device 1 are shown in fig. 2. The processing shown in fig. 2 is some processing realized by causing the CPU to execute a program stored in the memory. Fig. 2 shows each process implemented.

As shown in fig. 2, the steering control device 1 includes a steering-side control unit 50 that controls the supply of electric power to the steering-side motor 13. The steering-side control unit 50 includes a steering-side current sensor 54. The steering-side current sensor 54 detects a steering-side actual current value Ia obtained from a value of a phase current of the steering-side motor 13 flowing in a connection line between the steering-side control unit 50 and a phase motor coil of the steering-side motor 13. The steering side current sensor 54 obtains, as a current, a voltage drop of a shunt resistor connected to the source side of each switching element in an inverter (not shown) provided so as to correspond to the steering side motor 13. In fig. 2, each of the phase connection lines and the phase current sensors is shown in common for the purpose of convenience of description.

The steering control device 1 includes a steering-side control unit 60 that controls the supply of electric power to the steering-side motor 32. The steering side control unit 60 includes a steering side current sensor 66. The steering side current sensor 66 detects a steering side actual current value Ib obtained from the value of the phase current of the steering side motor 32 flowing in the connection line between the steering side control unit 60 and the phase motor coil of the steering side motor 32. The steering-side current sensor 66 obtains, as a current, a voltage drop of a shunt resistor connected to the source side of each switching element in an inverter (not shown) provided corresponding to the steering-side motor 32. In fig. 2, each of the phase connection lines and the phase current sensors is shown in common for convenience of description.

The steering control device 1 includes a vehicle speed calculation unit 200. The vehicle speed calculation unit 200 calculates the control vehicle speed V as a vehicle speed obtained by estimating a vehicle body speed that is a speed at which the vehicle actually travels. The vehicle body speed may also be said to be a speed sensed by an occupant of the vehicle. The wheel speeds Vfl, Vfr, Vrl, and Vrr and the stop lamp signal S are input to the vehicle speed calculation unit 200. The vehicle speed calculation unit 200 calculates a control vehicle speed V based on the wheel speeds Vfl, Vfr, Vrl, and Vrr and the stop lamp signal S. The function of the vehicle speed calculation unit 200 will be described in detail later. The obtained control vehicle speed V is output to the steering side control unit 50 and the steering side control unit 60 as one state variable for controlling the operation of the steering system 2. In this embodiment, the vehicle speed calculation unit 200 is implemented as one function of the steering side control unit 60. In this embodiment, the steering side control unit 60 corresponds to a vehicle speed calculation device. That is, the steering control device 1 including the steering-side control unit 60 corresponds to a vehicle speed calculation device.

Steering side control unit 50

The steering torque Th, the control vehicle speed V, the rotation angle θ a, the steering-side actual current value Ib, and a target pinion angle θ p, which will be described later, are input to the steering-side control unit 50. The steering-side control unit 50 controls the supply of electric power to the steering-side motor 13 based on the steering torque Th, the control vehicle speed V, the rotation angle θ a, the steering-side actual current value Ib, and the target pinion angle θ p.

The steering-side control unit 50 includes a steering angle calculation unit 51, a target reaction torque calculation unit 52, and a power supply control unit 53. The rotation angle θ a is input to the steering angle calculation unit 51. The steering angle calculation unit 51 converts the rotation angle θ a into a total angle in a range including a range exceeding 360 degrees, for example, by counting the number of rotations of the steering-side motor 13 from a steering neutral point, which is the position of the steering wheel 3 when the vehicle moves straight ahead. The steering angle calculation unit 51 calculates the steering angle θ s by multiplying the total angle obtained by the conversion by a conversion factor based on the rotation speed ratio of the speed reduction mechanism 14. The calculated steering angle θ s is output to the target reaction torque calculation unit 52. The steering angle θ s is output to a steering side control unit 60, that is, a steering angle ratio change control unit 62 which will be described later.

The steering torque Th, the control vehicle speed V, the steering-side actual current value Ib, the steering angle θ s, and a target pinion angle θ p, which will be described later, are input to the target reaction torque calculation unit 52. The target reaction torque calculation unit 52 calculates a target reaction torque Ts, which is a target reaction control value for the steering reaction force of the steering wheel 3 to be generated by the steering-side motor 13, based on the steering torque Th, the control vehicle speed V, the steering-side actual current value Ib, the steering angle θ s, and the target pinion angle θ p.

Specifically, the target reaction torque calculation unit 52 includes a steering force calculation unit 55 and an axial force calculation unit 56. The steering torque Th, the control vehicle speed V, and the steering angle θ s are input to the steering force calculation unit 55. The steering force calculation unit 55 calculates the steering force Tb based on the steering torque Th, the control vehicle speed V, and the steering angle θ s.

Specifically, as shown in fig. 3, the steering force calculation unit 55 includes a basic control value calculation unit 71 and a compensation value calculation unit 72. The steering torque Th and the control vehicle speed V are input to the basic control value calculation unit 71. The basic control value calculation unit 71 calculates a basic control value I1 based on the steering torque Th and the control vehicle speed V. The basic control value I1 is a control value calculated in association with the steering of the steering wheel 3. The basic control value I1 is a basic component of the steering force Tb, and is set so that the steering of the steering wheel 3 indicates a desired characteristic. For example, the basic control value calculation unit 71 calculates the basic control value I1 such that the absolute value of the basic control value I1 becomes larger as the absolute value of the steering torque Th becomes larger and as the control vehicle speed V becomes smaller, taking into account the assist gradient that is the ratio of the change in the basic control value I1 to the change in the steering torque Th. The obtained basic control value I1 is output to the adder 73.

The steering torque Th, the control vehicle speed V, and the steering angle θ s are input to the compensation value calculation unit 72. The compensation value calculation unit 72 calculates a return compensation value I2, a hysteresis compensation value I3, a damping compensation value I4, and an inertia compensation value I5, which will be described below, based on the steering torque Th, the control vehicle speed V, and the steering angle θ s. In addition to the above-described compensation values I2 through I5, although not shown in the drawings, the various compensation values include a phase retardation compensation value for performing phase compensation so as to retard the phase of the steering torque Th and a phase advance compensation value for performing phase compensation so as to advance the phase of the basic control value I1. The phase delay compensation value is used to adjust the auxiliary gradient. The phase advance compensation value is used to stabilize the system by suppressing the resonance characteristic. The various compensation values are compensation values for performing compensation such that the operation of the steering wheel 3 achieved based on the basic control value I1 indicates a desired characteristic.

The compensation value calculating unit 72 includes a return compensation value calculating unit 81, a hysteresis compensation value calculating unit 82, a damping compensation value calculating unit 83, and an inertia compensation value calculating unit 84. The steering torque Th, the control vehicle speed V, the steering angle θ s, and the steering speed ω s obtained from the differentiator 85 by differentiating the steering angle θ s are input to the return compensation value calculation unit 81. The return compensation value calculation unit 81 calculates a return compensation value I2 on the basis of the steering torque Th, the control vehicle speed V, the steering angle θ s, and the steering speed ω s. The return compensation value I2 is used to perform compensation for a return operation of the steering wheel 3 to the steering neutral position. The returning operation of the steering wheel 3 is associated with the self-aligning torque of the steered

wheels

5L and 5R, and the excess and deficiency of the self-aligning torque are compensated by the return compensation value I2. The return compensation value I2 is used to generate a torque in a direction in which the steering wheel 3 returns to the steering neutral position. The obtained return compensation value I2 is output to the adder 73.

The control vehicle speed V and the steering angle θ s are input to the hysteresis compensation value calculation unit 82. The hysteresis compensation value calculation unit 82 calculates a hysteresis compensation value I3 based on the control vehicle speed V and the steering angle θ s. The hysteresis compensation value I3 is used to perform compensation such that hysteresis characteristics due to friction at the time of operation of the steering wheel 3 are optimized. The hysteresis characteristic due to friction at the time of operation of the steering wheel 3 is associated with the mechanical friction component of the vehicle in which the steering system 2 is installed, and the hysteresis characteristic due to the mechanical friction component is optimized by compensation using the hysteresis compensation value I3. The hysteresis compensation value I3 has a hysteresis characteristic with respect to a change in the steering angle θ s. The obtained hysteresis compensation value I3 is output to the adder 73.

The control vehicle speed V and the steering speed ω s are input to the damping compensation value calculation unit 83. The damping compensation value calculation unit 83 calculates a damping compensation value I4 based on the control vehicle speed V and the steering speed ω s. The damping compensation value I4 is used to perform compensation such that minute vibrations generated in the steering wheel 3 are reduced. The reduction of the minute vibration generated in the steering wheel 3 is associated with the viscous component of the steering system 2, particularly the viscous component of the steering-side actuator 31, and the minute vibration in the steering wheel 3 is reduced by compensation with the damping compensation value I4. The damping compensation value I4 is used to generate a torque in a direction opposite to the direction in which the steering speed ω s is generated at that time. The obtained damping compensation value I4 is output to the adder 73.

The control vehicle speed V and the steering acceleration α s obtained from the differentiator 86 by differentiating the steering speed ω s are input to the inertia compensation value calculation unit 84. The inertia compensation value calculation unit 84 calculates an inertia compensation value I5 based on the control vehicle speed V and the steering acceleration α s. The inertia compensation value I5 is used to perform compensation so that a stuck feeling at the start of steering operation of the steering wheel 3 and a flow feeling (overshoot) at the end of steering operation are suppressed. The suppression of the stuck feeling at the start of the steering operation of the steering wheel 3 and the suppression of the flow feeling (overshoot) at the end of the steering operation are associated with the inertia component of the steering system 2, and the stuck feeling at the start of the steering operation of the steering wheel 3 and the flow feeling (overshoot) at the end of the steering operation are suppressed by performing compensation using the inertia compensation value I5. The inertia compensation value I5 is used to generate a torque in the direction in which the steering acceleration α s is generated in the case where the absolute value of the steering acceleration α s increases, for example, at the start of the steering wheel 3, and to generate a torque in the direction opposite to the direction in which the steering acceleration α s is generated in the case where the absolute value of the steering acceleration α s decreases, for example, at the end of the steering wheel 3. The obtained inertia compensation value I5 is output to the adder 73.

The adder 73 calculates the steering force Tb by adding the compensation values I2 through I5 to the basic control value I1. In addition to the compensation values I2 to I5, for example, phase retardation compensation values or phase advance compensation values are also added to the basic control value I1 and reflected therein. The obtained steering manipulation force Tb is output to the subtractor 57. The steering force Tb acts in the same direction as the steering direction of the driver. The steering force Tb is calculated as a value having the dimension of torque (N · m).

As shown in fig. 2, the control vehicle speed V, the steering-side actual current value Ib, and a target pinion angle θ p, which will be described later, are input to the axial force calculation unit 56. The axial force calculation unit 56 calculates the axial force F acting on the rack shaft 22 via the steered

wheels

5L and 5R based on the control vehicle speed V, the steering-side actual current value Ib, and the target pinion angle θ p.

Specifically, as shown in fig. 4, the axial force calculation unit 56 includes an angular axial force calculation unit 91, a current axial force calculation unit 92, and an axial force distribution ratio calculation unit 93. A target pinion angle θ p, which will be described later, and a control vehicle speed V are input to the angular axial force calculation unit 91. The angular axial force calculation unit 91 calculates the angular axial force Fr based on the target pinion angle θ p and the control vehicle speed V. The angular axial force Fr is an ideal value of an axial force defined by a model of the vehicle arbitrarily set. The angular axial force Fr is calculated as an axial force that does not reflect road surface information. The road surface information is information such as minute unevenness that does not affect the behavior of the vehicle in the lateral direction or a stepped portion that affects the behavior of the vehicle in the lateral direction. For example, the angular axial force calculation unit 91 calculates the angular axial force Fr such that the absolute value thereof increases as the absolute value of the target pinion angle θ p increases. The angular axial force calculation unit 91 calculates the angular axial force Fr such that the absolute value thereof increases as the control vehicle speed V increases. The angular axial force Fr is calculated as a value having a dimension of torque (N · m). The obtained angular axial force Fr is output to the multiplier 94.

The steering-side actual current value Ib is input to the current axial force calculation unit 92. The current axial force calculation unit 92 calculates a current axial force Fi based on the steering-side actual current value Ib. The current axial force Fi is an estimated value of an axial force actually acting on the rack shaft 22 that operates to steer the steered

wheels

5L and 5R, that is, an axial force actually transmitted to the rack shaft 22. The current axial force Fi is calculated as an axial force reflecting road surface information, for example. For example, based on the assumption that the torque applied to the rack shaft 22 by the steering-side motor 32 and the torque corresponding to the force applied to the rack shaft 22 via the steered

wheels

5L and 5R are balanced, the current axial force calculation unit 92 calculates the current axial force Fi such that the absolute value of the current axial force Fi increases as the absolute value of the steering-side actual current value Ib increases. The current axial force Fi is calculated as a value having a dimension of torque (N · m). The obtained current axial force Fi is output to the multiplier 95.

The control vehicle speed V is input to the axial force distribution ratio calculation unit 93. The axial force distribution ratio calculation unit 93 calculates an axial force distribution gain Di based on the control vehicle speed V. The axial force distribution gain Di is a distribution ratio of the current axial force Fi in a case where the angle axial force Fr and the current axial force Fi are summed at the distribution ratio to obtain the axial force F. The axial force distribution ratio calculation unit 93 includes an axial force distribution gain map in which a relationship between the control vehicle speed V and the axial force distribution gain Di is defined. The axial force distribution ratio calculation unit 93 calculates the axial force distribution gain Di using the map and using the control vehicle speed V as an input. The current axial force Fi is multiplied by the obtained axial force distribution gain Di, and is output to the adder 98 as the final current axial force Fim obtained from the multiplier 95. The subtractor 96 calculates an axial force distribution gain Dr by subtracting the axial force distribution gain Di from "1" stored in the storage unit 97. The obtained axial force distribution gain Dr is output to the multiplier 94. The axial force distribution gain Dr is a distribution ratio of the angular axial force Fr when the axial force F is obtained. That is, the axial force distribution gain Dr is calculated so that the sum with the axial force distribution gain Di is "1 (100%)". The distribution ratio includes the concept of a zero value, in which only one of the angular axial force Fr and the current axial force Fi is distributed to the axial force F. The storage unit 97 is a predetermined storage area of a memory not shown.

The angular axial force Fr obtained by the angular axial force calculation unit 91 is multiplied by the obtained axial force distribution gain Dr and output to the adder 98 as the final angular axial force Frm obtained by the multiplier 94. The summer 98 calculates the axial force F by adding the angular axial force Frm to the current axial force Fim (i.e., by summing the angular axial force Frm with the current axial force Fim). The axial force F acts in a direction opposite to the steering direction of the driver. The axial force F is calculated as a value having the dimension of torque (N · m). The obtained axial force F is output to the subtractor 57. The subtractor 57 calculates the target reaction torque Ts by subtracting the axial force F from the steering force Tb. The obtained target reaction torque Ts is output to the power supply control unit 53.

As shown in fig. 2, the target reaction torque Ts, the rotation angle θ a, and the steering-side actual current value Ia are input to the power supply control unit 53. The power supply control unit 53 calculates a current command value Ia for the steering-side motor 13 based on the target reaction torque Ts. The power supply control unit 53 calculates a difference between the current command value Ia and a current value on a d-q coordinate system obtained by converting the steering-side actual current value Ia based on the rotation angle θ a, and controls the supply of electric power to the steering-side motor 13 so that the difference is cancelled. The steering-side motor 13 generates a torque corresponding to the target reaction torque Ts. Therefore, the driver can be given an appropriate response feeling.

Steering side control unit 60

The steering side control unit 60 includes a pinion angle calculation unit 61, a steering angle ratio change control unit 62, a limit processing unit 63, a pinion angle feedback control unit (a "pinion angle feedback control unit" in fig. 2) 64, a power supply control unit 65, and a vehicle speed calculation unit 200.

The rotation angle θ b is input to the pinion angle calculation unit 61. The pinion angle calculation unit 61 converts the rotation angle θ b into a total angle in a range including a range exceeding 360 degrees, for example, by counting the number of rotations of the steering-side motor 32 from a rack neutral position, which is a position of the rack shaft 22 when the vehicle travels straight ahead. The pinion angle calculation unit 61 calculates the pinion angle θ p by multiplying the total angle obtained by the conversion by a conversion factor based on the reduction ratio of the transmission mechanism 33, the lead of the conversion mechanism 34, and the rotation speed ratio of the rack and pinion mechanism 24. The pinion angle θ p obtained in this way is output to the pinion angle feedback control unit 64.

The control vehicle speed V and the steering angle θ s are input to the steering angle ratio change control unit 62. The steering angle ratio change control unit 62 calculates a pre-limit target pinion angle θ pb by adding the adjustment value to the steering angle θ s. The pre-limited target pinion angle θ pb is a fundamental component of the final target pinion angle θ p. The steering angle ratio change control unit 62 changes an adjustment value for changing a steering angle ratio, which is a ratio of the target pinion angle θ pb to the steering angle θ s, in accordance with the control vehicle speed V. For example, the adjustment value is changed such that the change in the target pinion angle θ pb with respect to the steering angle θ s is larger in the case where the control vehicle speed V is small than in the case where the control vehicle speed V is large. There is a correlation between the steering angle thetas and the target pinion angle thetabpb. The pinion angle θ p is controlled based on a target pinion angle θ p, wherein the target pinion angle θ pb serves as a fundamental component of the target pinion angle θ p. Therefore, there is also a correlation between the steering angle θ s and the pinion angle θ p. The obtained target pinion angle θ pb is output to the restriction processing unit 63.

The control vehicle speed V and the target pinion angle θ pb are input to the limit processing unit 63. Specifically, as shown in fig. 5, the limit processing unit 63 includes a limit value calculation unit 101 and a protection processing unit 102.

The control vehicle speed V is input to the limit value calculation unit 101. Limit value calculation unit 101 calculates a limit value θ L for target pinion angle θ pb based on control vehicle speed V. The range of variation of the target pinion angle θ pb is limited by the limit value θ L. The limit value θ L is set based on a limit value that is determined according to the axial force characteristic of the vehicle to an angle that maintains a balance between the maximum output of the steering-side motor 32 and the axial force acting on the rack shaft 22. The axial force acting on the rack shaft 22 when steering the steered

wheels

5L and 5R differs according to the control vehicle speed V. For example, the limit value calculation unit 101 calculates the limit value θ L such that the absolute value of the limit value θ L decreases as the control vehicle speed V increases in the case where the axial force acting on the rack shaft 22 when steering the steered

wheels

5L and 5R is likely to be smaller in the case where the control vehicle speed V is relatively high than in the case where the control vehicle speed V is relatively low. The obtained limit value θ L is output to the protection processing unit 102.

The target pinion angle θ pb and the limit value θ L are input to the protection processing unit 102. The protection processing unit 102 performs a limiting process so that the target pinion angle θ pb is limited to the limit value θ L based on the limit value θ L. That is, the protection processing unit 102 compares the target pinion angle θ pb with the limit value θ L, and in the case where the absolute value of the target pinion angle θ pb is larger than the limit value θ L, the protection processing unit 102 calculates a value obtained by limiting the absolute value of the target pinion angle θ pb to the limit value θ L instead of the target pinion angle θ pb as the final target pinion angle θ p. In the case where the absolute value of the target pinion angle θ pb is equal to or smaller than the limit value θ L, the protection processing unit 102 calculates the target pinion angle θ pb obtained by the steering angle ratio change control unit 62 as the final target pinion angle θ p without any change. The obtained final target pinion angle θ p is output to the pinion angle feedback control unit 64. The target pinion angle θ p is output to the steering side control unit 50, that is, the axial force calculation unit 56.

As shown in fig. 2, the control vehicle speed V, the target pinion angle θ p, and the pinion angle θ p are input to the pinion angle feedback control unit 64. Specifically, as shown in fig. 6, the pinion angle feedback control unit 64 includes a proportional component calculation unit 111, an integral component calculation unit 112, and a differential component calculation unit 113.

The control vehicle speed V and the angle difference Δ θ p obtained from the subtractor 114 by subtracting the pinion angle θ p from the target pinion angle θ p are input to the proportional component calculation unit 111. Proportional component calculation section 111 calculates proportional gain Kp using proportional gain calculation section 121. The proportional gain calculation unit 121 calculates a proportional gain Kp based on the control vehicle speed V. The angular difference Δ θ p is multiplied by the obtained proportional gain Kp using a multiplier 122 to obtain a proportional component Tp, and the proportional component Tp is output to the adder 115.

The control vehicle speed V and the angle difference Δ θ p are input to the integral component calculation unit 112. The integral component calculation unit 112 calculates an integral gain Ki using the integral gain calculation unit 131. The integral gain calculation unit 131 calculates an integral gain Ki based on the control vehicle speed V. The angular difference Δ θ p is multiplied by the obtained integral gain Ki using a multiplier 132 to obtain an integral basic component Tib, and the integral basic component Tib is output to an adder 133. The adder 133 calculates, as the integral component Ti, an integral value obtained by adding the previous integral component Ti (-) to the integral basic component Tib calculated in the operation period. The previous integral component Ti (-) is an integral value obtained by repeatedly performing addition of the integral basic component Tib calculated up to the previous calculation period. The obtained integral component Ti is output to the adder 115.

The control vehicle speed V and the angle difference Δ θ p are input to the differential component calculation unit 113. The differential component calculation unit 113 calculates a differential gain Kd using the differential gain calculation unit 141. The angular velocity difference Δ ω p is multiplied by the obtained differential gain Kd using a multiplier 142 to obtain a differential component Td, and the differential component Td is output to the adder 115. The angular velocity difference Δ ω p is obtained by differentiating the angular difference Δ θ p using the differentiator 143.

The adder 115 calculates the steering force command value Tt by summing the proportional component Tp, the integral component Ti, and the differential component Td. The obtained steering force command value Tt is output to the power supply control unit 65.

The steering force command value Tt, the rotation angle θ b, and the steering-side actual current value Ib are input to the power supply control unit 65. The power supply control unit 65 calculates a current command value Ib for the steering-side motor 32 based on the steering force command value Tt. The power supply control unit 65 calculates a difference between the current command value Ib and a current value on a d-q coordinate system obtained by converting the steering-side actual current value Ib based on the rotation angle θ b, and controls the supply of electric power to the steering-side motor 32 so that the difference is cancelled out. Therefore, the steering-side motor 32 rotates by an angle corresponding to the steering force command value Tt.

Vehicle speed calculation unit 200

The function of the vehicle speed calculation unit 200 will be described in detail below. As shown in fig. 7, the vehicle speed calculation unit 200 includes a first vehicle speed calculation unit 201, a second vehicle speed calculation unit 202, and a vehicle speed distribution ratio calculation unit 203.

The wheel speeds Vfl, Vfr, Vrl, and Vrr are input to the first vehicle speed calculation unit 201. Specifically, as shown in fig. 8, the first vehicle speed calculation unit 201 includes a first maximum value calculation unit 211, a second maximum value calculation unit 212, a first minimum value calculation unit 213, a second minimum value calculation unit 214, a third minimum value calculation unit 215, a third maximum value calculation unit 216, and a fourth minimum value calculation unit 217.

The front wheel speeds Vfl and Vfr are input to the first maximum value calculation unit 211. The first maximum value calculation unit 211 performs a calculation such that the larger one of the front wheel speeds Vfl and Vfr is extracted as a front wheel maximum value Vfmax. The front wheel maximum value Vfmax is the maximum value among the wheel speed of the right front wheel and the wheel speed of the left front wheel. The obtained front wheel maximum value Vfmax is output to the third minimum value calculation unit 215.

The rear wheel speeds Vr1 and Vrr are input to the second maximum value calculation unit 212. The second maximum value calculation unit 212 performs calculation such that the larger one of the rear wheel speeds Vr1 and Vrr is extracted as the rear wheel maximum value Vrmax. The rear wheel maximum value Vrmax is the maximum value among the wheel speed of the right rear wheel and the wheel speed of the left rear wheel. The obtained rear wheel maximum value Vrmax is output to the third minimum value calculation unit 215.

The front wheel speeds Vfl and Vfr are input to the first minimum value calculation unit 213. The first minimum value calculation unit 213 performs a calculation such that the smaller one of the front wheel speeds Vfl and Vfr is extracted as a front wheel minimum value Vfmin. The front wheel minimum value Vfmin is the minimum value among the wheel speed of the right front wheel and the wheel speed of the left front wheel. The obtained front wheel minimum value Vfmin is output to the third maximum value calculation unit 216.

The rear wheel speeds Vrl and Vrr are input to the second minimum value calculation unit 214. The second minimum value calculation unit 214 performs calculation such that the smaller one of the rear wheel speeds Vrl and Vrr is extracted as a rear wheel minimum value Vrmin. The rear wheel minimum Vrmin is the minimum value among the wheel speed of the right rear wheel and the wheel speed of the left rear wheel. The obtained rear wheel minimum value Vrmin is output to the third maximum value calculation unit 216.

The wheel maximum values Vfmax and Vrmax are input to the third minimum value calculation unit 215. The third minimum value calculating unit 215 performs calculation such that the smaller one of the wheel maximum values Vfmax and Vrmax is extracted as the first wheel speed intermediate value Vmid 1. The first wheel speed intermediate value Vmid1 is an intermediate value having the second largest size or the third largest size among the wheel speeds of the four wheels including the right and left front wheels and the right and left rear wheels. That is, the first wheel speed intermediate value Vmid1 is a value obtained by excluding the maximum value and the minimum value from the wheel speeds of the four wheels. The obtained first wheel speed intermediate value Vmid1 is output to the fourth minimum value calculation unit 217.

The wheel minimum values Vfmin and Vrmin are input to a third maximum value calculation unit 216. The third maximum value calculation unit 216 performs calculation such that the larger one of the wheel minimum values Vfmin and Vrmin is extracted as the second wheel speed intermediate value Vmid 2. The second wheel speed intermediate value Vmid2 is an intermediate value having the second largest magnitude or the third largest magnitude among the wheel speeds of the four wheels. That is, the second wheel speed intermediate value Vmid2 is a value obtained by excluding the maximum value and the minimum value from the wheel speeds of the four wheels. The obtained second wheel speed intermediate value Vmid2 is output to the fourth minimum value calculation unit 217.

The wheel speed intermediate values Vmid1 and Vmid2 are input to the fourth minimum value calculating unit 217. The fourth minimum value calculating unit 217 performs calculation such that the smaller one of the wheel speed intermediate values Vmid1 and Vmid2 is extracted as the first vehicle speed V1. The first vehicle speed V1 is an intermediate value having the third largest among the wheel speeds of the four wheels. The obtained first vehicle speed V1 is output to the multiplier 206.

In the case where there is a wheel that spins relative to the ground contact surface due to acceleration of the vehicle, that is, in the case where there is a wheel that is in a slip state, each of the wheel speeds of the four wheels having the first and second large magnitudes is more likely to be information obtained from the wheel that is in the slip state. This is because, in the case where there are wheels in a slipping state, there is a high possibility that the number of wheels in a slipping state is not one but a pair of right and left front wheels or a pair of right and left rear wheels is in a slipping state. On the other hand, for example, even in the case where the rotation state of some wheels is the slip state, the wheel speed having the third largest magnitude is more likely to be information obtained from wheels that are not in the slip state. That is, the wheel speed having the third largest magnitude is unlikely to be a value obtained from the wheel in the slipping state. The wheel speed having the third largest magnitude is a value close to the average of the wheel speeds of the four wheels. In this case, in the absence of the wheel in the slipping state, the difference between the wheel speed having the third largest magnitude and the vehicle body speed is smaller than the difference between the wheel speed having the fourth largest magnitude and the vehicle body speed. In this embodiment, the first vehicle speed V1 obtained as the wheel speed having the third largest magnitude is a value having the following functions: in the case where the rotation state of some wheels is assumed to be a slip state, the difference from the vehicle body speed is reduced.

In this embodiment, in the first vehicle speed calculation unit 201, extracting a wheel speed having the third largest among the wheel speeds of the four wheels corresponds to an extraction function, i.e., a first extraction function. In the first vehicle speed calculation unit 201, calculating the wheel speed having the third largest among the wheel speeds of the four wheels as the first vehicle speed V1 corresponds to a calculation function.

The rear wheel speeds Vr1 and Vrr are input to the second vehicle speed calculation unit 202. Specifically, as shown in fig. 9, rear wheel speeds Vrl and Vrr of two wheels extracted from among the wheel speeds Vfl, Vfr, Vrl, and Vrr of the four wheels are input to the second wheel speed calculation unit 202. The second vehicle speed calculation unit 202 calculates a rear wheel added value Vadd, which is an added value (sum value) of the rear wheel speeds Vrl and Vrr obtained from the adder 221 by summing the rear wheel speeds Vrl and Vrr. The obtained rear wheel added value Vadd is multiplied by a predetermined gain "0.5 (1/2)" using the gain multiplier 222, and is output to the multiplier 207 as the second vehicle speed V2. That is, the second vehicle speed V2 is calculated as an average value of the rear wheel speeds Vr1 and Vrr.

From the viewpoint of the running stability of the vehicle, the right and left rear wheels among the four wheels are predetermined in the design of the vehicle as wheels that are unlikely to be in a so-called locked state. The locked state is a state in which the wheel does not rotate relative to the ground contact surface due to braking of the vehicle. That is, for example, even in the case where the rotation state of some of the wheels is the locked state, the wheel speeds obtained from the right and left rear wheels are more likely to be information obtained from the wheels that are not in the locked state. That is, the wheel speeds obtained from the right and left rear wheels are unlikely to be the values obtained from the wheels in the locked state. In this case, unless all the four wheels are in the locked state, the difference between the wheel speed obtained from the right and left rear wheels and the vehicle body speed is small. In this embodiment, the second vehicle speed V2 obtained from the right and left rear wheels is a value having the following functions: in the case where the rotation state of some wheels is assumed to be the locked state, the difference from the vehicle body speed is reduced.

In this embodiment, in the second vehicle speed calculation unit 202, the rear wheel speeds Vrl and Vrr obtained from the right and left rear wheels that are determined in the design of the vehicle to be unlikely to fall into the locked state and extracted from among the wheel speeds of the four wheels are input corresponding to an extraction function, i.e., a second extraction function. In the second vehicle speed calculation unit 202, calculating the average value of the rear wheel speeds Vr1 and Vrr among the wheel speeds of the four wheels as the second vehicle speed V2 corresponds to a calculation function.

As shown in fig. 7, the vehicle speed distribution ratio calculation unit 203 includes a vehicle speed gain calculation unit 204 and a gradual change processing unit 205. The stop lamp signal S is input to the vehicle speed gain calculation unit 204. The vehicle speed gain calculation unit 204 calculates a basic vehicle speed distribution gain Dv2b based on the stop lamp signal S. The vehicle speed gain calculation unit 204 calculates the basic vehicle speed distribution gain Dv2b as "1 (100%)" in the case where the stop lamp signal S indicates the on state, and calculates the basic vehicle speed distribution gain Dv2b as "0 (0%)" in the case where the stop lamp signal S indicates the off state. The obtained base vehicle speed distribution gain Dv2b is subjected to gradual change processing by the gradual change processing unit 205.

Specifically, in the case where the base vehicle speed distribution gain Dv2b is switched between "1" and "0", the gradual-change processing unit 205 performs gradual-change processing with respect to time on the base vehicle speed distribution gain Dv2 b. In the case where the base vehicle speed distribution gain Dv2b is switched between "1" and "0", the gradual-change processing unit 205 obtains the difference between the base vehicle speed distribution gain Dv2b calculated before the switching and the base vehicle speed distribution gain Dv2b calculated after the switching, that is, the gradual-change processing unit 205 obtains "1" and calculates the difference as the offset value. In this case, the gradual-change processing unit 205 calculates the vehicle speed distribution gain Dv2 that has undergone the gradual-change process by shifting the post-switching base vehicle speed distribution gain Dv2b to the pre-switching base vehicle speed distribution gain Dv2b by an offset value. Then, the gradual-change processing unit 205 performs gradual-change processing of changing the vehicle speed distribution gain Dv2 such that the vehicle speed distribution gain Dv2 becomes the original value by gradually decreasing the offset value with the passage of time after the switching. Therefore, even in the case where the basic vehicle speed distribution gain Dv2b is switched between "1" and "0", an abrupt change in the vehicle speed distribution gain Dv2 is suppressed. In the case where the base vehicle speed distribution gain Dv2b is not switched between "1" and "0" and there is no offset value, the gradual-change processing unit 205 calculates the base vehicle speed distribution gain Dv2b calculated by the vehicle speed gain calculation unit 204 as the vehicle speed distribution gain Dv2 that has undergone the gradual-change process. In the case where the control vehicle speed V is obtained by summing the first vehicle speed V1 and the second vehicle speed V2 at the distribution ratio, the vehicle speed distribution gain Dv2 is used as the distribution ratio of the second vehicle speed V2.

The second vehicle speed V2 is multiplied by the obtained vehicle speed distribution gain Dv2 using the multiplier 207, and is output to the adder 208 as the final second vehicle speed V2 m. The subtractor 209 calculates a vehicle speed distribution gain Dv1 by subtracting the vehicle speed distribution gain Dv2 from "1" stored in the storage unit 210. The vehicle speed distribution gain Dv1 is a distribution ratio of the first vehicle speed V1 in the case where the control vehicle speed V is obtained. That is, the vehicle speed distribution gain Dv1 is calculated such that the sum with the vehicle speed distribution gain Dv2 becomes "1 (100%)". The allocation ratio in this embodiment includes the concept of zero value, in which only one of the first vehicle speed V1 and the second vehicle speed V2 is allocated to the control vehicle speed V.

Specifically, regarding the vehicle speed distribution gains Dv1 and Dv2, in the case where the stop lamp signal S indicates the on state, the vehicle speed distribution gain Dv2 is "1" and the vehicle speed distribution gain Dv1 is "0". In a deceleration state of the vehicle in which the stop lamp signal S indicates the on state, the rotation state of some wheels may be assumed to be the locked state. That is, in the case where it is assumed that the rotation state of some of the wheels is the locked state, this means that only the second vehicle speed V2 is assigned (allocated) to the control vehicle speed V, that is, the first vehicle speed V1 is not assigned (not allocated).

In addition, regarding the vehicle speed distribution gains Dv1 and Dv2, in the case where the stop lamp signal S indicates the off state, the vehicle speed distribution gain Dv2 is "0" and the vehicle speed distribution gain Dv1 is "1". In the case where the stop lamp signal S indicates that the vehicle in the off state is in a state including an acceleration state instead of a deceleration state, the rotation state of some wheels may be assumed to be a slip state. That is, in the case where it is assumed that the rotation state of some of the wheels is the slip state, this means that only the first vehicle speed V1 is assigned (allocated) to the control vehicle speed V, that is, the second vehicle speed V2 is not assigned (not allocated).

The first vehicle speed V1 is multiplied by the obtained vehicle speed distribution gain Dv1 using the multiplier 206, and is output to the adder 208 as the final first vehicle speed V1 m. The storage unit 210 is a predetermined storage area of a memory not shown.

The adder 208 calculates the control vehicle speed V by adding the second vehicle speed V2m to the first vehicle speed V1 m. The obtained control vehicle speed V is output to the steering angle ratio change control unit 62, the limit processing unit 63, and the pinion angle feedback control unit 64. The control vehicle speed V is output to the steering side control unit 50, i.e., the steering force calculation unit 55 and the axial force calculation unit 56.

The operation of this embodiment will be described below. According to this embodiment, the wheel speed obtained from the wheels assumed to be rotating in a state where the influence causing the difference from the vehicle body speed may be small, among the four wheels rotating in a state where there are large and small influences causing the difference from the vehicle body speed, is positively considered in calculating the control vehicle speed V. This is achieved by the functions of the first vehicle speed calculation unit 201 and the second vehicle speed calculation unit 202 of the vehicle speed calculation unit 200.

Here, the wheel speed obtained from the wheel in the slip state as the rotation state of the wheel may be larger than the wheel speed obtained from the wheel not in the slip state, and the possibility that the wheel speed obtained from the wheel in the slip state is different from the vehicle body speed is high. On the other hand, the wheel speed classified into the small value, that is, having the third large size and the fourth large size, in the case where the values of the wheel speeds of the four wheels are classified according to the sizes thereof, is low in the possibility of being the value obtained from the wheel in the slip state.

Therefore, the first vehicle speed calculation unit 201 is configured to calculate the first vehicle speed V1 obtained by extracting the wheel speed having the third largest among the wheel speeds of the four wheels. In the case where the vehicle is in a state including an acceleration state, not a deceleration state, the obtained first vehicle speed V1 is reflected in the control vehicle speed V by the vehicle speed calculation unit 200. In this case, assuming that the rotation state of some of the wheels is a slip state, the difference between the vehicle body speed and the control vehicle speed V can be reduced.

For example, the wheel speed obtained from the wheel in the locked state as the rotation state of the wheel may be smaller than the wheel speed obtained from the wheel not in the locked state, and the possibility that the wheel speed obtained from the wheel in the locked state is different from the vehicle body speed is high. On the other hand, from the viewpoint of the running stability of the vehicle, the two rear wheels are determined as wheels that are unlikely to be in a locked state in the design of the vehicle.

Therefore, the second vehicle speed calculation unit 202 is configured to calculate the second vehicle speed V2 obtained by extracting the wheel speeds of the right and left rear wheels from among the wheel speeds of the four wheels. In the case where the vehicle is in the decelerating state, the obtained second vehicle speed V2 is reflected in the control vehicle speed V by the vehicle speed calculation unit 200. In this case, assuming that the rotation state of some of the wheels is the locked state, the difference between the vehicle body speed and the control vehicle speed V can be reduced.

The advantages of this embodiment will be described below. (1-1) the vehicle speed calculation unit 200 according to the embodiment need not employ a method of performing filtering processing when obtaining the control vehicle speed V as a method of reducing the difference between the vehicle body speed and the control vehicle speed V. In this case, it is possible to achieve both reduction of the difference between the vehicle body speed and the control vehicle speed V and suppression of a decrease in the ability to follow the change in the control vehicle speed V in various controls in the vehicle using the control vehicle speed V.

(1-2) the first vehicle speed calculation unit 201 is configured to extract a wheel speed having the third largest among the wheel speeds of the four wheels. Therefore, even in the case where there is a wheel in a slipping state among some wheels, the wheel speed obtained from the wheel not in a slipping state can be positively considered in calculating the control vehicle speed V. This is effective for reducing the difference between the vehicle body speed and the control vehicle speed V.

(1-3) the second vehicle speed calculation unit 202 is configured to extract the wheel speeds of the right and left rear wheels among the four wheels. Therefore, even in the case where there is a wheel in a locked state among some wheels, the wheel speed obtained from the wheel not in the locked state can be positively considered in calculating the control vehicle speed V. This is effective for reducing the difference between the vehicle body speed and the control vehicle speed V.

(1-4) the vehicle speed calculation unit 200 is configured to calculate the control vehicle speed V by summing the first vehicle speed V1 obtained by the first vehicle speed calculation unit 201 and the second vehicle speed V2 obtained by the second vehicle speed calculation unit 202 in a distribution ratio. Therefore, the control vehicle speed V may be calculated based on the first vehicle speed V1 assuming that there is a wheel in a slipping state, and the control vehicle speed V may be calculated based on the second vehicle speed V2 assuming that there is a wheel in a locked state. Therefore, the difference between the vehicle body speed and the control vehicle speed V can be effectively reduced.

(1-5) the possibility that there is a wheel in a slipping state or a locked state changes depending on whether the vehicle is in a decelerating state, and the vehicle speed calculation unit 200 is configured to change the distribution ratio depending on whether the vehicle is in a decelerating state. When the distribution ratio is actually changed, the control vehicle speed V obtained as a result of the calculation may suddenly change between before and after the change of the distribution ratio. Therefore, the vehicle speed calculation unit 200 adopts a configuration in which the gradual change processing unit 205 is provided in the vehicle speed distribution ratio calculation unit 203. In this case, even when the distribution ratio is changed, it is possible to suppress an abrupt change in the vehicle speed obtained as a result of the calculation between before and after the change.

(1-6) the vehicle speed calculation unit 200 according to the embodiment is implemented as a function of the steering control device 1 configured to control the operation of the steering system 2 using the control vehicle speed V. In this case, it is possible to achieve both reduction of the difference between the vehicle body speed and the control vehicle speed V and suppression of a decrease in the ability to follow the change in the control vehicle speed V in various controls in the steering control device 1 using the control vehicle speed V.

Second embodiment

A vehicle speed calculation device and a control device for a vehicle according to a second embodiment will be described below with reference to the drawings. Differences from the first embodiment will be mainly described below. The same elements as in the first embodiment will be denoted by the same reference numerals, and repeated description thereof will be omitted.

In this embodiment, information indicating the validity of each of the wheel speeds Vfl, Vfr, Vrl, and Vrr, that is, information indicating whether each of the wheel speeds Vfl, Vfr, Vrl, and Vrr is abnormal or not is added. For example, in the case where the wheel speeds Vfl, Vfr, Vrl, and Vrr are output to the steering control device 1, when there is an abnormal value, the brake control device 45 outputs an abnormal signal Se as information indicating which value is abnormal. In this case, the brake control device 45 generates the abnormality signal Se when any of the

wheel speed sensors

47l, 47r, 48l, and 48r has a value that is less likely to pass the comparison with the previous value. Determining whether each of the wheel speeds Vfl, Vfr, Vrl, and Vrr is abnormal may be implemented as a function of the vehicle speed calculation unit 200. In this case, the configuration associated with the abnormal signal Se may be deleted.

First vehicle speed calculation unit 201

Specifically, as shown in fig. 10, the first vehicle speed calculation unit 201 includes an abnormal wheel speed replacement unit 218 in addition to the above-described configuration in the first embodiment.

The wheel speeds Vfl, Vfr, Vrl, and Vrr and the abnormality signal Se are input to the abnormal wheel speed replacement unit 218. In the case where an abnormality signal Se indicating that any of the wheel speeds Vfl, Vfr, Vrl, and Vrr is abnormal is input, the abnormal wheel speed replacement unit 218 performs replacement processing for replacing the abnormal wheel speed with a predetermined fixed value Re. The fixed value Re is set to the negative value of the maximum value where the absolute value is maximum in the wheel speed range. That is, the fixed value Re represents a value smaller than any other wheel speed, that is, the minimum value among the wheel speeds of the four wheels. In this case, the abnormal wheel speed replacement unit 218 outputs the fixed value Re for the abnormal wheel speed to the first maximum value calculation unit 211, the second maximum value calculation unit 212, the first minimum value calculation unit 213, and the second minimum value calculation unit 214 based on the abnormal signal Se.

For example, in the case where the wheel speed abnormal based on the abnormality signal Se is the wheel speed Vrr of the right rear wheel, the abnormal wheel speed replacement unit 218 outputs the fixed value Re as the value of the rear wheel speed Vrr to the first maximum value calculation unit 211, the second maximum value calculation unit 212, the first minimum value calculation unit 213, and the second minimum value calculation unit 214. In this case, the second maximum value calculation unit 212 is prevented from calculating the rear wheel speed Vrr, which is a fixed value Re that is the minimum value among the wheel speeds of the four wheels, as the rear wheel maximum value Vrmax. On the other hand, the second minimum value calculation unit 214 calculates a rear wheel speed Vrr of a fixed value Re, which is the minimum value among the wheel speeds of the four wheels, as a rear wheel minimum value Vrmin. Here, the third maximum value calculating unit 216 is prevented from calculating the rear wheel minimum value Vrmin, which is the rear wheel speed Vrr, as the second wheel intermediate value Vmid 2.

According to this embodiment, operations and advantages similar to those in the first embodiment are achieved. According to this embodiment, the following advantages are additionally achieved. (2-1) the first vehicle speed calculation unit 201 is prevented from reflecting the abnormal wheel speed based on the abnormality signal Se in the first vehicle speed V1. This is effective for reducing the difference between the vehicle body speed and the control vehicle speed V.

(2-2) in this embodiment, the second vehicle speed calculation unit 202 may be configured to implement the same function as that of the abnormal wheel speed replacement unit 218. For example, the rear wheel speeds Vrl and Vrr and the abnormality signal Se are input to the second vehicle speed calculation unit 202. In this case, the second wheel speed calculation unit 202 may be configured to replace the average value of the rear wheel speeds Vr1 and Vrr with the average value of the values of the wheel speeds other than the abnormal wheel speed based on the abnormal signal Se. Therefore, the second vehicle speed calculation unit 202 is prevented from reflecting the abnormal wheel speed based on the abnormal signal Se in the second vehicle speed V2.

The above embodiment may be modified as follows. The following embodiments may be combined unless a technical conflict arises. In the above embodiment, the stop lamp signal S input to the vehicle speed calculation unit 200 may be replaced with a state variable as appropriate as long as the state variable has a correlation with the deceleration state of the vehicle. Examples of the state variables include a rate of change Δ V in the speed of the vehicle. The rate of change Δ V in the speed of the vehicle is obtained by differentiating the control vehicle speed V calculated up to the previous calculation cycle. Examples of the state variables include a longitudinal acceleration Cx and a vertical acceleration Cz generated in the vehicle. As shown by the two-dot chain line in fig. 1, the longitudinal acceleration Cx and the vertical acceleration Cz are obtained as a result of detection from an acceleration sensor 230, such as a gyro sensor, provided in the vehicle. Examples of the state variables include longitudinal loads Fxl and Fxr, vertical loads Fzl and Fzr, pitch moments MFyl and Mfyr, and roll moments MFzl and MFzr calculated based on the forces acting on the steered

wheels

5L and 5R. As shown by the two-dot chain lines in fig. 1, the longitudinal loads Fxl and Fxr, the vertical loads Fzl and Fzr, the pitch moments MFyl and MFyr, and the roll moments MFzl and MFzr are obtained as results of detection from the left front tire force sensor 231L and the right front tire force sensor 231R that are realized as one function of the sensor hubs corresponding to the steered

wheels

5L and 5R. The same applies to the longitudinal loads Rx1 and Rxr, the vertical loads Rz1 and Rzr, the pitch moments MRy1 and MRyr, and the roll moments MRz1 and MRzr, which are forces acting on the left and right rear wheels. As shown by the two-dot chain lines in fig. 1, the longitudinal loads Rx1 and Rxr, the vertical loads Rz1 and Rzr, the pitch moments MRy1 and MRyr, and the roll moments MRz1 and MRzr are obtained as a result of detection from the left rear tire force sensor 2321 and the right rear tire force sensor 232r that are implemented as one function of sensor hubs corresponding to the left rear wheel and the right rear wheel. Examples of the state variable include an operation signal Sb or a brake pressure Pb of a brake pedal Bp installed in the vehicle. As shown by the solid line in fig. 1, the operation signal Sb or the brake pressure Pb is obtained from information that changes in association with the operation of the brake pedal Bp. Various state variables may be used to determine whether the vehicle is in a decelerating state.

In the above embodiment, the vehicle speed calculation unit 200 may have a function of determining whether the vehicle is in an acceleration state, that is, whether the vehicle is being driven, instead of determining whether the vehicle is in a deceleration state. In this case, for example, the operation signal Sa or the accelerator operation amount Oa of the accelerator pedal Ap installed in the vehicle may be input to the vehicle speed calculation unit 200, i.e., the vehicle speed gain calculation unit 204, instead of the stop lamp signal S. As shown by the two-dot chain line in fig. 1, the operation signal Sa or the accelerator operation amount Oa is obtained from information that changes in association with the accelerator pedal Ap. For example, in the case where the value indicated by the operation signal Sa or the accelerator operation amount Oa indicates that the vehicle is in an acceleration state, the vehicle speed gain calculation unit 204 may calculate the basic vehicle speed distribution gain Dv2b as "zero". In the case where the value indicated by the operation signal Sa or the accelerator operation amount Oa indicates that the vehicle is in a state including a decelerating state, instead of an accelerating state, the vehicle speed gain calculation unit 204 may calculate the base vehicle speed distribution gain Dv2b as "1 (100%)". In this embodiment, the operation signal Sa or the accelerator operation amount Oa may be appropriately replaced with a state variable having a correlation with the acceleration state of the vehicle. Examples of the state variables include a rate of change Δ V of a control vehicle speed V of the vehicle. Examples of the state variables include a longitudinal acceleration Cx and a vertical acceleration Cz generated in the vehicle. Examples of the state variables include longitudinal loads Fxl and Fxr, vertical loads Fzl and Fzr, pitch moments MFyl and MFyr, and roll moments MFzl and MFzr calculated based on the forces acting on the steered

wheels

5L and 5R. The same applies to the longitudinal loads Rx1 and Rxr, the vertical loads Rz1 and Rzr, the pitch moments MRy1 and MRyr, and the roll moments MRz1 and MRzr, which are forces acting on the left and right rear wheels. Examples of the state variables include a difference between an output speed Vtm of a transmission TM mounted in the vehicle and a wheel speed obtained based on rear wheel speeds Vrl and Vrr. As shown by the two-dot chain line in fig. 1, the output speed Vtm is obtained from information that changes in association with the operation of the transmission TM mounted in the vehicle, so that power for running the vehicle is transmitted to the right and left rear wheels as drive wheels. Various state variables may be used to determine whether the vehicle is in an accelerating state. The vehicle speed calculation unit 200 according to the embodiment may have a function of determining whether the vehicle is in a decelerating state in addition to the function of determining whether the vehicle is in an accelerating state, which has been described above in the above-described embodiments and the like.

In the above-described embodiment, for example, the brake control device 45 may execute, as the control based on the control vehicle speed V, the control for changing the yaw rate Y generated in the vehicle regardless of the state of the steering mechanism 4, that is, regardless of the steering manipulation by the driver. For example, the control vehicle speed V obtained by the function of the vehicle speed calculation unit 200 of the steering control device 1 may be input to the brake control device 45. In this embodiment, the brake control device 45 corresponds to a control device for a vehicle. The braking device corresponds to an in-vehicle device. The control based on the control vehicle speed V may be control of a rear wheel steering device for steering the right and left rear wheels. In this case, the rear wheel steering device corresponds to an in-vehicle device.

In the above embodiment, the brake control device 45 may be configured to have the function of the vehicle speed calculation unit 200. In this case, the function of the vehicle speed calculation unit 200 may be deleted from the steering control device 1, and the control vehicle speed V may be input via the brake control device 45. In this embodiment, the brake control means 45 corresponds to vehicle speed calculation means.

In the above-described embodiment, the function of the vehicle speed calculation unit 200 may be implemented as the function of the steering-side control unit 50. In the case where the function of the vehicle speed calculation unit 200 is implemented as the function of the steering control device 1, the function may be implemented as the function of a control unit other than the

control units

50 and 60. The function of the vehicle speed calculation unit 200 may be implemented as the function of a control device other than the steering control device 1 and the brake control device 45.

In the above embodiment, the function of the gradual change processing unit 205 may be deleted from the vehicle speed calculation unit 200. In this case, the vehicle speed calculation unit 200 may be configured to calculate one of the first vehicle speed V1 and the second vehicle speed V2 as the control vehicle speed V according to the stop lamp signal S. Therefore, the function of the vehicle speed gain calculation unit 204 and the function of the gradual change processing unit 205 may be deleted from the vehicle speed calculation unit 200.

In the first embodiment, the first vehicle speed calculation unit 201 may extract the fourth largest wheel speed, that is, the smallest wheel speed, among the wheel speeds of the four wheels. In this case, the same advantages as (1-1) to (1-6) in the first embodiment can also be achieved.

In the first embodiment, in a case where there is a wheel in a slip state and the wheel in the slip state is assumed to be one wheel, the first vehicle speed calculation unit 201 may extract the second largest wheel speed among the wheel speeds of the four wheels. In this case, the first vehicle speed calculation unit 201 may be configured to include a maximum value calculation unit that extracts the larger of the wheel speed intermediate values Vmid1 and Vmid2 as the first vehicle speed V1, instead of the fourth minimum value calculation unit 217.

In the above embodiment, the second wheel speed calculation unit 202 may calculate one of the rear wheel speeds Vr1 and Vrr as the second wheel speed V2 instead of the average of the rear wheel speeds Vr1 and Vrr.

In the first embodiment, the vehicle speed calculation unit 200 has at least one function of the first vehicle speed calculation unit 201 and the second vehicle speed calculation unit 202. For example, the second vehicle speed calculation unit 202 may be deleted from the vehicle speed calculation unit 200, and the first vehicle speed V1 may be calculated as the control vehicle speed V. In this case, at least effective reflection of the value obtained from the wheel not in a slip state when the control vehicle speed V is calculated can be achieved. The first vehicle speed calculation unit 201 may be deleted from the vehicle speed calculation unit 200, and the second vehicle speed V2 may be calculated as the control vehicle speed V. In this case, at least effective reflection of the value obtained from the wheel not in the locked state at the time of calculation of the control vehicle speed V can be achieved. The same applies to the second embodiment.

In the second embodiment, the fixed value Re may be replaced with the following value as appropriate as long as the value can be prevented from being extracted as the first vehicle speed V1 by the first vehicle speed calculation unit 201. For example, it may be prevented that the value extracted as the first vehicle speed V1 by the first vehicle speed calculation unit 201 may be a value obtained by simply replacing the actual wheel speed at that time with a negative value or a zero value.

In the above embodiment, the basic control value calculation unit 71 may not use the control vehicle speed V and may use a combination of other elements as long as the basic control value I1 is calculated using at least one state variable associated with the operation of the steering wheel 3. The steering torque Th in the above-described embodiment may not be used as the state variable associated with the operation of the steering wheel 3.

In the above embodiment, the steering-manipulation-side control unit 50 may calculate the target reaction torque Ts using, as the steering manipulation force Tb, a value calculated by performing torque feedback control for matching the steering manipulation torque Th with the target steering manipulation torque calculated based on the steering manipulation torque Th and/or the axial force F. In this case, the proportional component, the integral component, and/or the derivative component for the torque feedback control may be changed based on the control vehicle speed V.

In the above embodiment, the compensation value calculating unit 72 may calculate at least one compensation value of the compensation values I2 through I5. As long as the return compensation value I2 is calculated using at least the steering angle θ s and the steering speed ω s, the return compensation value calculation unit 81 may not use the control vehicle speed V or the steering torque Th and may use a combination of other elements. As long as the hysteresis compensation value I3 is calculated using at least the steering angle θ s, the hysteresis compensation value calculation unit 82 may not use the control vehicle speed V and may use a combination of other elements such as the steering torque Th. The hysteresis compensation value calculation unit 82 may calculate the hysteresis compensation value I3 using the steering speed ω s instead of the steering angle θ s in consideration of hysteresis characteristics with respect to the steering speed ω s. As long as at least the steering speed ω s is used to calculate the damping compensation value I4, the damping compensation value calculation unit 83 may not use the control vehicle speed V and may use a combination of other elements such as the steering torque Th. As long as at least the steering acceleration α s is used to calculate the inertia compensation value I5, the inertia compensation value calculation unit 84 may not use the control vehicle speed V and may use a combination of other elements such as the steering torque Th.

In the above embodiment, as long as the angular axial force Fr is calculated using at least the target pinion angle θ p, the angular axial force calculation unit 91 may not use the control vehicle speed V and may use a combination of other elements. The angular axial force calculation unit 91 may use the pinion angle θ p instead of the target pinion angle θ p.

In the above embodiment, as long as the current axial force Fi is calculated using at least the steering side actual current value Ib, the current axial force calculation unit 92 may use a combination of other elements such as the control vehicle speed V. The current axial force calculation unit 92 may use the obtained current command value instead of the steering-side actual current value Ib to cancel the difference from the current value on the d-q coordinate system obtained by converting the steering-side actual current value Ib based on the rotation angle θ b.

In the above-described embodiment, instead of or in addition to controlling the vehicle speed V, the axial force distribution ratio calculation unit 93 may calculate the axial force distribution gain Di using another element such as the pinion angle θ p, the target pinion angle θ p, the steering angle θ s, or a steering speed obtained by differentiating the pinion angle θ p.

In the above embodiment, the angular axial force calculation unit 91 or the current axial force calculation unit 92 may be deleted from the axial force calculation unit 56. In this case, the axial force distribution ratio calculation unit 93 may be deleted. The angular axial force Fr calculated by the angular axial force calculation unit 91 or the current axial force Fi calculated by the current axial force calculation unit 92 is output to the subtractor 57.

In the above embodiment, the axial force calculation unit 56 may have a function of calculating an axial force for transmitting the state of the steering mechanism 6 to the driver, in addition to the angle axial force calculation unit 91 and the current axial force calculation unit 92. The state of the steering mechanism 6 may be, for example, a state in which the steering limit of the steering wheel 3, i.e., the steering limit of the steered

wheels

5L and 5R, has been reached. The state of the steering mechanism 6 may be, for example, a state that deviates (changes) based on the relationship of the steering angle ratio between the steering state of the steering wheel 3 and the steering state of the steered

wheels

5L and 5R.

In the above-described embodiment, the steering angle ratio change control unit 62 may calculate the pre-limit target pinion angle θ pb by performing adjustment of the frequency characteristic on the target pinion angle calculated by adding the adjustment value and the steering angle θ s. In this case, the adjustment state of the frequency characteristic may be changed according to the control vehicle speed V.

In the above embodiment, the steering angle ratio change control unit 62 may change the adjustment value for changing the steering angle ratio, based on the yaw rate Y, the lateral acceleration Cy, and the like calculated based on the result of detection from the acceleration sensor 230, in addition to the control vehicle speed V.

In the above-described embodiment, the steering side control unit 60 may include a limiting processing unit that performs limiting processing such that the target pinion angular velocity obtained by differentiating the target pinion angle θ pb is limited by a limited value. In this case, the limit processing unit changes the limit value of the target pinion angular speed in accordance with the control vehicle speed V.

In the above embodiment, the proportional component calculating unit 111 in the pinion angle feedback control unit 64 may change the relationship of the output and the input of the proportional component calculating unit 111 based on the control vehicle speed V, instead of changing the proportional component Tp based on the control vehicle speed V using the proportional gain Kp. The integral component calculation unit 112 may change the relationship of the output to the input of the integral component calculation unit 112 based on the control vehicle speed V, instead of changing the integral component Ti based on the control vehicle speed V using the integral gain Ki. The differential component calculation unit 113 may change the relationship of the output and the input of the differential component calculation unit 113 based on the control vehicle speed V, instead of changing the differential component Td based on the control vehicle speed V using the differential gain Kd.

In the above-described embodiment, the pinion angle feedback control unit 64 performs PID control using the proportional component Tp, the integral component Ti, and the differential component Td as the angle feedback control, but the present invention is not limited thereto, and for example, PI control may be performed. The execution mode of the pinion angle feedback control unit 64 may be modified as appropriate.

In the above embodiment, the gradual-change processing unit 205 may have the following functions: the offset value is gradually decreased by a value that varies according to the vehicle state, rather than gradually decreasing the offset value over time. The vehicle state includes, for example: the difference between the control vehicle speed V obtained at the vehicle speed distribution gain Dv2 before being switched using the vehicle speed distribution gain Dv2, the control vehicle speed V obtained at the vehicle speed distribution gain Dv2 after being switched using the vehicle speed distribution gain Dv2, and the control vehicle speed V between before and after being switched using the vehicle speed distribution gain Dv 2. The vehicle state includes, for example, state variables having a correlation with the acceleration-deceleration state of the vehicle. The vehicle state includes, for example, a lateral acceleration Cy in the vehicle obtained as a result of detection from the acceleration sensor 230. The vehicle state includes, for example, the lateral loads Fyl and Fyr, the roll moments MFzl and MFzr, and the yaw moments MFxl and MFxr obtained as a result of detection from the front-wheel tire force sensors 231l and 231 r. The same applies to the lateral loads Ryl and Ryr, the roll moments MRzl and MRzr, and the yaw moments MRxl and MRxr obtained as a result of detection from the rear wheel tire force sensors 232l and 232 r. The vehicle state includes, for example, a yaw rate Y calculated based on the result of detection from the acceleration sensor 230. The vehicle state includes, for example, a slip angle SA that is a lateral slip angle of the steered

wheels

5L and 5R calculated based on the result of detection from the acceleration sensor 230. The offset value may be gradually decreased by a value that varies according to the vehicle state using various vehicle states.

In the above embodiment, the gradual-change processing unit 205 may have the following functions: the offset value is gradually decreased by a value that changes according to the steering state, rather than gradually decreasing the offset value over time. The steering state includes, for example, a steering angle θ s. The steering state includes, for example, a target steering angle that is a target value of the steering angle θ s calculated based on the steering torque Th. The steering state includes, for example, an estimated steering angle obtained by estimating the steering angle θ s based on the steering angle θ s and the steering torque Th. The steering manipulation state includes, for example, a driving support control value Ad for providing an instruction to change the steering angle of the steered

wheels

5L and 5R when the driving support control is executed. As shown by the two-dot chain line in fig. 1, the driving support control value Ad is obtained from a driving support control device 233 provided in the vehicle separately from the steering control device 1. The driving support control device 233 controls the operation of the steering mechanism 6, that is, the steering system 2, so that various driving supports for improving the comfort of the vehicle can be performed. The driving support includes prevention of lane departure of the vehicle, support of emergency avoidance, and alternative driving when the vehicle is stopped. The steering state includes, for example, a steering speed ω s, a target steering speed obtained by differentiating the target steering angle, an estimated steering speed obtained by differentiating the estimated steering angle, and a rate of change in the driving support control value obtained by differentiating the driving support control value Ad. The steering state includes, for example, a steering torque Th. The steering state includes, for example, an estimated steering torque obtained by estimating the steering torque Th based on the steering angle θ s and the steering torque Th. The steering state includes, for example, a steering torque differential value obtained by differentiating the steering torque Th and an estimated steering torque differential value obtained by differentiating the estimated steering torque. The offset value may be gradually decreased by a value that varies according to the steering state using various steering states.

In the above embodiment, the gradual-change processing unit 205 may have the following functions: the offset value is gradually decreased by a value that changes according to the steering state, rather than gradually decreasing the offset value over time. The steering state includes, for example, the steering angle of the steered

wheels

5L and 5R and the pinion angle θ p. As shown by the two-dot chain line in fig. 1, the steering angle of the steered

wheels

5L and 5R is obtained as a result of detection from a stroke sensor 234 that detects the axial displacement X of the rack shaft 22. The steering state includes, for example, a target pinion angle θ p and an angle obtained in calculating the target pinion angle θ p, for example, a target pinion angle θ pb. The steering state includes, for example, a driving support control value Ad. The steering state includes, for example, a pinion angular velocity obtained by differentiating the pinion angle θ p, a target pinion angular velocity obtained by differentiating the target pinion angle θ p or an angle obtained in calculating the target pinion angle θ p, and a rate of change in the driving support control value obtained by differentiating the driving support control value Ad. The offset value may be gradually decreased by a value varying according to the steering state using various steering states.

In the above-described embodiment, the steering angle calculation unit 51 may calculate the steering angle θ s by reflecting the twist in the rotation angle θ a by addition/subtraction of the twist in consideration of the twist of the steering shaft 11 according to the steering torque Th.

In the above-described embodiment, the result of detection from the steering sensor provided in the steering shaft 11 so that the rotation angle of the steering shaft 11 can be detected can be used as the steering angle θ s. In the above-described embodiment, the steering-side motor 32 may take, for example, a configuration in which the steering-side motor 32 is arranged coaxially with the rack shaft 22, or a configuration in which the steering-side motor 32 is connected to a pinion shaft via a worm and a worm wheel, the pinion shaft and the rack shaft 22 constituting a rack-and-pinion mechanism.

In the above-described embodiments, the steering control device 1 may be configured as a processing circuit including (1) one or more processors operating according to a computer program (software), (2) one or more dedicated hardware circuits such as Application Specific Integrated Circuits (ASICs) that perform at least some of the various processes, or (3) a combination thereof. The processor includes a CPU and memories such as a RAM and a ROM, and the memories store program codes or commands configured to cause the CPU to execute processing. Memory, i.e., non-transitory computer-readable media, includes all available media that can be accessed by a general purpose or special purpose computer. The same applies to the brake control device 45.

In the above-described embodiment, the steering system 2 employs a link-less structure in which the steering mechanism 4 and the steering mechanism 6 are normally mechanically disconnected from each other, but the present invention is not limited thereto, and the steering system may employ a structure in which the steering mechanism 4 and the steering mechanism 6 may be mechanically disconnected by a clutch. The steering system 2 may be an electric power steering system that applies an assist force as a force for assisting the steering operation of the driver. In this case, the steering wheel 3 is mechanically connected to the pinion shaft 21 via the steering shaft 11.

The vehicle mounted with the steering system 2 according to the above-described embodiment may employ a so-called FF system in which a driving torque for rotationally driving the right and left front wheels is generated by a driving source mounted on the front side of the vehicle. In this case, the right and left front wheels are the drive wheels. The vehicle mounted with the steering system 2 may employ a so-called four-wheel drive system in which a drive torque for rotationally driving the four wheels individually is generated using power generated by a drive source mounted on the front side of the vehicle. In this case, each of the four wheels is a driving wheel. In the vehicle mounted with the steering system 2, the position where the driving source for generating the driving torque is mounted, for example, the rear side or the center in the longitudinal direction of the vehicle, is not particularly limited.

Claims

1. A vehicle speed calculation device characterized by comprising:

a vehicle speed calculation unit (200) configured to calculate, as a state variable for controlling an in-vehicle device configured to operate to implement various functions provided in a vehicle, a control vehicle speed obtained by estimating a vehicle body speed that is a speed at which the vehicle actually travels,

wherein the vehicle speed calculation unit (200) is configured to include:

an extraction function that extracts, from among a plurality of wheel speeds of a plurality of wheels, at least one wheel speed obtained from at least one wheel that is assumed to rotate in a state where an influence that causes a difference from the vehicle body speed is likely to be small; and

a calculation function that calculates the control vehicle speed based on at least one wheel speed extracted by the extraction function.

2. The vehicle speed calculation device according to claim 1, characterized in that the extraction function is configured to extract at least one wheel speed classified into at least one small value in a case where the values of the plurality of wheel speeds are classified according to magnitudes of the values of the plurality of wheel speeds.

3. The vehicle speed calculation device according to claim 2, characterized in that the extraction function is configured to extract at least one wheel speed of at least one wheel that is determined in the design of the vehicle to be unlikely to fall into a locked state, the locked state of each of the plurality of wheels being a state in which the wheel does not rotate relative to a ground contact surface even while the vehicle is traveling.

4. The vehicle speed calculation device according to claim 3, characterized in that the extraction function includes: a first extraction function of extracting at least one wheel speed classified into the at least one small value in a case where the values of the plurality of wheel speeds are classified according to magnitudes of the values of the plurality of wheel speeds, and a second extraction function of extracting at least one wheel speed of at least one wheel determined in design of the vehicle to be unlikely to fall into the locked state, and

wherein the vehicle speed calculation unit (200) is configured to calculate the control vehicle speed based on at least one of a first vehicle speed obtained from the at least one wheel speed extracted by the first extraction function and a second vehicle speed obtained from the at least one wheel speed extracted by the second extraction function.

5. The vehicle speed calculation device according to claim 4, characterized in that the vehicle speed calculation unit (200) is configured to further include: a vehicle speed distribution function that sums a plurality of vehicle speeds including a first vehicle speed obtained by the first extraction function and a second vehicle speed obtained by the second extraction function at a predetermined distribution ratio; and

wherein the vehicle speed distribution function includes: a function of changing the distribution ratio according to an acceleration-deceleration state of the vehicle, and a function of gradually changing the distribution ratio when changing the distribution ratio.

6. A control device for a vehicle, characterized by comprising a vehicle speed calculation device according to any one of claims 1 to 5, wherein the control device is configured to control operation of the vehicle-mounted device using a control vehicle speed obtained by the vehicle speed calculation device.